Lung injury is a common disease, and acute lung injury (ALI) severely affects the human health. ALI is an injury to alveolar epithelial cells and capillary endothelial cells caused by various direct and indirect insults, and leads to diffuse pulmonary interstitial edema and alveolar edema, and also to acute hypoxic respiratory insufficiency which is an early stage of acute respiratory distress syndrome (ARDS). Pulmonary fibrosis (PF) is an interstitial lung disease having very poor prognosis and severely affecting the quality of life of patients, and is one of the most serious diseases in the respiratory system. At present, studies have shown that PF results from lung injury, characterized by migration, attachment and proliferation of fibroblasts in the alveolar space. In recent years the mortality of early-stage ALI has been considerably improved, but late-stage PF directly and indirectly results in death of patients. It was found that 55% of lung biopsy from ALI deaths showed severe PF.
Dictamnusdasycarpus Turcz is a Traditional Chinese drug. It is isolated from Dictamnusdasycarpus root bark and has a strong special smell. Dictamnusdasycarpus Turcz. tastes bitter, has a cold nature, follows the spleen, stomach and bladdermeridian, and is effective in dispelling wind pathogen and eliminating dampness pathogen, clearing away heat-toxicity, relieving itching, and disinfecting insects. Obacunone is a limonoid extracted from Dictamnusdasycarpus Turcz, having a formula of C26H30O7 and a structure of formula (I) below.

Research has shown that obacunone exhibits an anti-tumor effect. A study on human colon cancer cells (SW480) showed that obacunone induced cell apoptosis by activating cytochrome C, and suppressed growth of tumor cells by activating p21 to arrest the cell cycle at phases G2/M and G1. A study on human pancreatic cancer cells (Panc-28) demonstrated that obacunone induced apoptosis of tumor cells by activating p53. Furthermore, obacunone also has an effect of inhibiting activity of arginase and reciprocally increasing NO production through enhancing stabilization of the endothelial NO synthase dimer, and thus can produce a certain therapeutic effect on cardiovascular diseases caused by endothelial functional disorder. However, a function of obacunone in prevention or treatment of lung injury and pulmonary fibrosis has not been reported yet.